Battery Booster Packs

Hi, I've been advised that starting a Motor Home with a flat battery with a booster pack can damage the vehicles electrics (Computers) Vehicle is a 2010  Mercedes Sprinter.

Agreed - it is best avoided, if possible. There are some situations where it just isn't avoidable (e.g. dead battery on the side of a fast road, which should be very rare), but it's better to remove, recharge and replace if you can, or recharge in situ. If you have to recharge with an industrial fast-charger it's best to disconnect the battery from the vehicle electrics as well, as they can apply much higher than normal charging voltage.

Some parts seem to be more vulnerable than others - on a VW T5 it's the ABS brake controller - and that no doubt varies from make to make.

Dealers do it all the time to the vehicles sat on their forecourts. They can’t keep every one of them connected to smart chargers.

Tinwheeler wrote:Dealers do it all the time to the vehicles sat on their forecourts. They can’t keep every one of them connected to smart chargers.

Probably true, and the chances of causing a failure are probably very low indeed - but the parts are so ridiculously expensive if you do cause one to fail that it is worth avoiding. On a T5, the ABS controller is roughly a £2000 part, and that's before it's been fitted and coded...

Roopert wrote:

Tinwheeler wrote:Dealers do it all the time to the vehicles sat on their forecourts. They can’t keep every one of them connected to smart chargers.

Probably true, and the chances of causing a failure are probably very low indeed - but the parts are so ridiculously expensive if you do cause one to fail that it is worth avoiding. On a T5, the ABS controller is roughly a £2000 part, and that's before it's been fitted and coded...

I don’t expect it to be a problem if used only as a last resort as most of us would but regular use might be a different matter.

Thanks for the replies. Agree a cranking output of these units is high and as pointed out car electrical components are eye watering expensive.

Are the jump starting points under the bonnet provided for just this purpose??

PLOUGHLIN wrote:Are the jump starting points under the bonnet provided for just this purpose??

Indeed they are.

Yes, I think most Merc Sprinters have a positive battery connection under the bonnet. I've used it once to charge up the vehicle battery using a smart charger. There was a warning light on the dash but a little reset procedure extinguished the light eventually. Probably illuminated when the battery was low. Thinking about it now the battery was possibly drained leaving the fridge door open with the selection left on battery?

I can't speak for the Merc but our Peugeot handbook advised against battery charging via the under bonnet connectors.   

Thinking laterally.....

None of this would be necessary with 80+w solar on roof.
Both batteries more or less guaranteed full 365 days / yr!!!

Agreed Ian. Fortunately or unfortunately which ever way you view it. Yes I have a solar panel fitted but my M/H is kept under a large car port at home. However periodical driving out does keep the batteries up. However as I stated earlier I think maybe leaving the fridge open and selected to battery position may have caused the vehicle battery drain? Further invest. Cheers J C.

Unless your fridge is a 12v compressor type it will not work on 12V unless the engine is running. I would expect your van to have a Domestic or Thetford 3 way fridge rendering 12v usage impossible unless engine is running.

The fridge control panel and interior light are usually a permanent live feed from the leisure battery to cope with running on gas off grid so would not drain the vehicle battery. The fridge motor runs as per Ron's description.

Thanks all for confirmation of the fridges power supply. Vehicle battery seems to behaving now.

I was told not to jump start a modern vehicle with the doner vehicle engine running, as the engine starts it is hit with the output of 2 alternators,

Molly3 wrote:I was told not to jump start a modern vehicle  with the doner vehicle engine running, as the engine starts it is hit with the output of 2 alternators,

MB instructions include "run the donor vehicle's engine at idling speed", which has been my understanding for all vehicles.